var websocket = null;   

//判断当前浏览器是否支持WebSocket   
if ('WebSocket' in window) {   
    websocket = new WebSocket("ws://localhost:8081/BaiduFace/websocket");   
} else {   
    alert('当前浏览器不支持websocket！请更换浏览器！');  
}   

//连接发生错误的回调方法   
websocket.onerror = function () {   
    setMessageInnerHTML("WebSocket连接发生错误");   
};  

//连接成功建立的回调方法  
websocket.onopen = function () {   
    setMessageInnerHTML("WebSocket连接成功");   
} ;  
    
//接收到消息的回调方法   
websocket.onmessage = function (event) {   
    setMessageInnerHTML(event.data);   
};  

//连接关闭的回调方法  
websocket.onclose = function () {   
    setMessageInnerHTML("WebSocket连接关闭");   
};  
//监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。  
window.onbeforeunload = function () {   
    closeWebSocket();   
};


//将消息显示在网页上   
function setMessageInnerHTML(innerHTML) {   
    document.getElementById('checkinMsg').innerHTML += innerHTML + '<br/>';   
}   
//关闭WebSocket连接   
function closeWebSocket() {   
    websocket.close();   
}   
//发送消息   
function send(msg) {   
    websocket.send(msg);   
} 